1. Field of the Invention
This invention relates to irrigation control systems, and more particularly to a system in which a multi-station controller can be operated from a remote location.
2. Description of the Prior Art
There are many large irrigation systems which employ a large number of widely separated valves to irrigate an extended area. Examples of such installations include farms, golf courses and large real estate development projects, in which a large number of stations may be employed. These systems generally employ a master controller which communicates with the various station valve by means of wire or radio. The controller can typically be programmed to operate each of the valves at desired intervals and for desired periods of time.
One of the principal problems in servicing such systems is that the maintenance person must do a lot of walking back and forth between the various stations and the central controller to turn one station at a time on and off for observation and servicing. In large systems the great majority of service time is often spent just walking (or driving if a suitable vehicle is available), rather than actually servicing the irrigation hardware. This waste of time is both costly and inefficient.
In an attempt to reduce the servicing time wasted in travelling back and forth between the controller and valves, a remote control device has been developed which permits the service person to exercise the controller and turn the valves on and off from a remote location, generally at or near a valve. The system is disclosed in U.S. Pat. No. 4,185,650 to Neves et al. Initially, the central controller is programmed to cycle through a predetermined sequence of stations for normal operation. Thus, each station is turned on and off in turn in the predetermined sequence, until the entire area has been watered. The service person is provided with a radio transmitter, which communicates with a corresponding receiver at the central controller. The transmitter can transmit on two different frequencies, one for advancing the controller through its station cycle to the desired station, and the other for turning the station on and off. To exercise any particular valve, the service person must first transmit at the station cycling frequency to advance the controller through its cycle, one station at a time. When the desired station has been reached, he then switches to the second frequency to turn it on.
While the system disclosed in the Neves patent is an improvement over the prior technique of physically travelling back and forth between the master controller and the various stations, its mode of operation is limited and can be somewhat inefficient. For example, if the central controller is set to the tenth station in a thirty-six station irrigation system and it is desired to operate the ninth station, the controller must be cycled up from the tenth station and all the way through the thirty-four intervening stations until it reaches the desired ninth station. This can be a time-consuming procedure which mitigates some of the advantage that could otherwise be obtained with the system.